Daniel Barthélémy

A dynamic model of plant growth with interactions between development and functional mechanisms to study plant structural plasticity related to trophic competition

BACKGROUND AND AIMSnThe strong influence of environment and functioning on plant organogenesis has been well documented by botanists but is poorly reproduced in most functional-structural models. In this context, a model of interactions is proposed between plant organogenesis and plant functional mechanisms.nnnMETHODSnThe GreenLab model derived from AMAP models was used. Organogenetic rules give the plant architecture, which defines an interconnected network of organs. The plant is considered as a collection of interacting sinks that compete for the allocation of photosynthates coming from sources. A single variable characteristic of the balance between sources and sinks during plant growth controls different events in plant development, such as the number of branches or the fruit load.nnnKEY RESULTSnVariations in the environmental parameters related to light and density induce changes in plant morphogenesis. Architecture appears as the dynamic result of this balance, and plant plasticity expresses itself very simply at different levels: appearance of branches and reiteration, number of organs, fructification and adaptation of ecophysiological characteristics.nnnCONCLUSIONSnThe modelling framework serves as a tool for theoretical botany to explore the emergence of specific morphological and architectural patterns and can help to understand plant phenotypic plasticity and its strategy in response to environmental changes.

Modelling architecture and growth patterns of Posidonia oceanica

Abstract The architecture and growth pattern of Posidonia oceanica was studied near Cannes, France in the Mediterranean from 80 samples collected at 6xa0m depth. Mathematical models were constructed in order to quantify the distribution of internodes within growth units from different morphological types of axes and branching orders. The results revealed that the frequency distribution of the number of internodes per growth unit on plagiotropic axes changed according to branching order, passing from a Poisson distribution on order-1 axes, to a combination of a Poisson and a binomial distribution on order-2 axes, to a binomial distribution on order-3 axes. The production of internodes per growth unit on orthotropic axes followed a binomial frequency distribution. The distribution of internodes produced by transitional-plagiotropic growth units was binomial despite the visual plagiotropic aspect of these units. The model shows that each year two statistically independent series of branches, with different probabilities according to branching order, occur in P. oceanica . The results are consistent with growth being regulated by an internal biological clock, which emits three signals during the course of the year.

Pl@ntNet mobile app

Pl@ntNet is an image sharing and retrieval application for the identification of plants, available on iPhone and iPad devices. Contrary to previous content-based identification applications it can work with several parts of the plant including flowers, leaves, fruits and bark. It also allows integrating users observations in the database thanks to a collaborative workflow involving the members of a social network specialized on plants. Data collected so far makes it one of the largest mobile plant identification tool.

A look inside the Pl@ntNet experience

Pl@ntNet is an innovative participatory sensing platform relying on image-based plants identification as a mean to enlist non-expert contributors and facilitate the production of botanical observation data. One year after the public launch of the mobile application, we carry out a self-critical evaluation of the experience with regard to the requirements of a sustainable and effective ecological surveillance tool. We first demonstrate the attractiveness of the developed multimedia system (with more than 90K end-users) and the nice self-improving capacities of the whole collaborative workflow. We then point out the current limitations of the approach towards producing timely and accurate distribution maps of plants at a very large scale. We discuss in particular two main issues: the bias and the incompleteness of the produced data. We finally open new perspectives and describe upcoming realizations towards bridging these gaps.

The imageCLEF plant identification task 2013

This paper presents a synthesis of ImageCLEF 2013 plant identification task, a system-oriented testbed dedicated to the evaluation of image-based plant identification technologies. With 12 participating groups coming from over 9 countries and 33 submitted runs, the 2013 campaign confirmed the increasing interest of the multimedia community in ecology-related challenges (respectively 10 and 11 groups crossed the finish line in 2011 and 2012). Contrary to the two previous years that were exclusively focused on leaf images, the coverage of the 2013 task was extended to six different types of view of the plant (flower, bark, fruit, entire, dots) and significantly more plant species. This synthesis presents the resources and assessments of task, summarizes the retrieval approaches employed by the participating groups, and provides an analysis of the main evaluation results.

Multi-organ plant identification

This paper presents a new interactive web application for the visual identification of plants based on collaborative pictures. Contrary to previous content-based identification methods and systems developed for plants that mainly relied on leaves, or in few other cases on flowers, it makes use of five different organs and plants views including habit, flowers, fruits, leaves and bark. Thanks to an interactive and visual query widget, the tagging process of the different organs and views is as simple as drag-and-drop operations and does not require any expertise in botany. All training pictures used by the system were continuously collected during one year through a crowdsourcing application that was set up in the scope of a citizen sciences initiative. System-oriented and human-centered evaluations of the application show that the results are already satisfactory and therefore very promising in the long term to identify a richer flora.

Annual shoot-growth in Nothofagus antarctica (G. Forster) Oersted (Nothofagaceae) from northern Patagonia

Abstractu2002The growth dynamics of annual shoots of Nothofagus antarctica shrubs from northern Patagonia was studied. The pattern of extension of the shoots derived from the three most distal buds of 100 parent shoots was registered. Weekly measurements and observations of extending shoots were carried out during the 1996–1997 growth season. The date of shoot extension initiation was less variable than the date of shoot extension cessation. Extension curves had an asymmetrically sigmoid outline. Most extension took place uninterruptedly between mid-September 1996 and the end of January 1997. Extension rate reached its highest value in the second half of the extension period. Leaf unfolding rate had a peak early in the extension period and fluctuated irregularly later on. The apical meristem of all shoots died by the end of shoot extension. In general terms, shoot length, diameter, leaf number and extension duration decreased from the first to the third position from the parent shoot’s apex, although exceptions to this pattern were found. Shoot extension rate was affected by maximum and minimum daily temperatures but not by the amount of precipitation during the extension period. The size of a bud was not related to the size of the shoot derived from it. The size of shoots in the third position from the apex was related to parent shoot size; this was not the case for more distal shoots.

Pl@ntNet Mobile 2014: Android port and new features

This paper presents several improvements of Pl@ntNet1, an image sharing and retrieval application for identifying plants [6]: (i) ported to most android platforms (ii) three times more data (iii) exploiting metadata as well as visual content in the identification process (iv) a new multi-plant-organ, multi-image and multi-feature merging strategy with separate indexes for each visual feature (v) integrating cross-languages functions. This paper also presents the new results achieved by our system in the ImageCLEF 2013 plant identification task and in real-world user trials.

The Genus Cecropia: A Biological Clock to Estimate the Age of Recently Disturbed Areas in the Neotropics

Forest successional processes following disturbance take decades to play out, even in tropical forests. Nonetheless, records of vegetation change in this ecosystem are scarce, increasing the importance of the chronosequence approach to study forest recovery. However, this approach requires accurate dating of secondary forests, which until now was a difficult and/or expensive task. Cecropia is a widespread and abundant pioneer tree genus of the Neotropics. Here we propose and validate a rapid and straightforward method to estimate the age of secondary forest patches based on morphological observations of Cecropia trees. We found that Cecropia-inferred ages were highly correlated with known ages of the forest. We also demonstrate that Cecropia can be used to accurately date disturbances and propose twenty-one species distributed all over the geographical range of the genus as potential secondary forest chronometer species. Our method is limited in applicability by the maximal longevity of Cecropia individuals. Although the oldest chronosequence used in this study was 20 years old, we argue that at least for the first four decades after disturbance, the method described in this study provides very accurate estimations of secondary forest ages. The age of pioneer trees provides not only information needed to calculate the recovery of carbon stocks that would help to improve forest management, but also provides information needed to characterize the initial floristic composition and the rates of species remigration into secondary forest. Our contribution shows how successional studies can be reliably and inexpensively extended without the need to obtain forest ages based on expensive or potentially inaccurate data across the Neotropics.

Comparative morphology of annual shoots in seedlings of five #Nothofagus# species from Argentinian Patagonia

Abstract Morphological features of seedlings were compared between five Nothofagus species from Patagonia: N. antarctica (Forst. F.) Oerst., N. dombeyi (Mirb.) Oerst, N. nervosa (Phil.) Dim. et Mil., N. obliqua (Mirb.) Oerst. and N. pumilio (Poepp. et Endl.) Krasser. Annual shoots of 1- to 3-year-old seedlings collected from natural communities were observed and the distribution of their length and number of internodes analysed. Each seedling produced one shoot each year. Leaves are alternate in all cases except for the cotyledons (which are always opposite) and the first two leaves after the cotyledons (which have, depending on the species, a high or low probability of being opposite to each other). Shoot length and number of internodes depended on the year and on the species concerned. Shoot length was more variable than internode number both within and between species. The probability of shoot apex death after shoot elongation may be high or low depending on the species and the age of the seedling.